The present invention relates generally to a system and method of optimizing a transcritical vapor compression system by maximizing the system heating capacity.
Chlorine containing refrigerants have been phased out in most of the world due to their ozone destroying potential. Hydrofluorocarbons (HFCs) have been used as replacement refrigerants, but these refrigerants still have high global warming potential.
“Natural” refrigerants, such as carbon dioxide and propane, have been proposed as replacement fluids. Carbon dioxide can be used as a refrigerant in automotive air conditioning systems and other heating and cooling applications. Carbon dioxide has a low critical point, which causes most air conditioning systems utilizing carbon dioxide as a refrigerant to run transcritically, or partially above the critical point, under most conditions.
A vapor compression system must be able to provide enough heating capacity to meet the load requirements during the winter when the outdoor air temperature is the lowest. For a given set of operating conditions, there is a high side pressure value which maximizes the coefficient of performance. A different high side pressure value for the same set of operating conditions maximizes the heating capacity. The high side pressure is generally selected to optimize the coefficient of performance. The coefficient of performance is very sensitive to the high side pressure when the high side pressure of the system is set below the high side pressure that optimizes the coefficient of performance. However, the coefficient of performance becomes insensitive to the high side pressure when the high side pressure of the system is set above the optimal high side pressure.
In prior vapor compressions systems, the vapor compression system is oversized to achieve sufficient heating capacity in low ambient conditions. A drawback to oversizing a vapor compression system is that it is expensive and requires more space.
Hence, there is a need in the art for a system and method of optimizing the heating capacity of a vapor compression system as well as overcoming the disadvantages of the prior art.